﻿using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace CommandLib
{
    /// <summary>
    /// 对称加密类
    /// </summary>
    public class DesHelper
    {
        /// <summary>
        /// 密文
        /// </summary>
        private const string DesKey = "abcd1234";
        /// <summary>
        /// 向量值
        /// </summary>
        private readonly static byte[] IV = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
        /// <summary>
        /// DES 加密(数据加密标准，速度较快，适用于加密大量数据的场合)
        /// </summary>
        /// <param name="EncryptString">待加密的密文</param>
        /// <param name="EncryptKey">加密的密钥</param>
        /// <returns>returns</returns>
        public static string DESEncrypt(string EncryptString, string EncryptKey = null)
        {

            if (string.IsNullOrEmpty(EncryptString)) { throw (new Exception("密文不得为空")); }

            if (string.IsNullOrEmpty(EncryptKey))
            {
                EncryptKey = DesKey;
            }

            if (EncryptKey.Length < 8) { throw (new Exception("密钥长度不低于8位")); }

            EncryptKey = EncryptKey.Substring(0, 8);
            string m_strEncrypt = string.Empty;
            var m_DESProvider = DES.Create();
            try
            {

                byte[] m_btEncryptString = Encoding.UTF8.GetBytes(EncryptString);
                MemoryStream m_stream = new MemoryStream();
                CryptoStream m_cstream = new CryptoStream(m_stream, m_DESProvider.CreateEncryptor(Encoding.UTF8.GetBytes(EncryptKey), IV), CryptoStreamMode.Write);
                m_cstream.Write(m_btEncryptString, 0, m_btEncryptString.Length);
                m_cstream.FlushFinalBlock();
                m_strEncrypt = Convert.ToBase64String(m_stream.ToArray());
                m_stream.Dispose();
                m_cstream.Dispose();
            }

            catch (Exception) { throw; }

            finally { m_DESProvider.Clear(); }

            return m_strEncrypt;

        }




        /// <summary>
        /// DES 解密(数据加密标准，速度较快，适用于加密大量数据的场合)
        /// </summary>
        /// <param name="DecryptString">待解密的密文</param>
        /// <param name="DecryptKey">解密的密钥</param>
        /// <returns>returns</returns>
        public static string DESDecrypt(string DecryptString, string DecryptKey = null)
        {

            if (string.IsNullOrEmpty(DecryptString)) { throw (new Exception("密文不得为空")); }
            if (string.IsNullOrEmpty(DecryptKey))
            {
                DecryptKey = DesKey;
            }
            if (DecryptKey.Length < 8) { throw (new Exception("密钥不低于8位")); }
            DecryptKey = DecryptKey.Substring(0, 8);
            string m_strDecrypt = string.Empty;
            var m_DESProvider = DES.Create();
            try
            {

                byte[] m_btDecryptString = Convert.FromBase64String(DecryptString);
                var m_stream = new MemoryStream();
                var m_cstream = new CryptoStream(m_stream, m_DESProvider.CreateDecryptor(Encoding.UTF8.GetBytes(DecryptKey), IV), CryptoStreamMode.Write);
                m_cstream.Write(m_btDecryptString, 0, m_btDecryptString.Length);
                m_cstream.FlushFinalBlock();
                m_strDecrypt = Encoding.UTF8.GetString(m_stream.ToArray());
                m_stream.Dispose();
                m_cstream.Dispose();
            }
            catch (Exception) { throw; }
            finally { m_DESProvider.Clear(); }
            return m_strDecrypt;

        }

    }
}
